基于压电时间反演法的螺栓松动检测研究

Bolt Looseness Detection Based on Piezoelectric Time Reversal Method

针对螺栓联接松动问题,研究了基于压电时间反演法的螺栓轴向力检测技术。采用压电材料分别作为激发器和传感器产生并接收超声波信号;利用时间反演技术的自适应聚焦效果及能有效提高信号信噪比的特性,将采集到的响应信号在时域上反演,作为激励信号再次发出,并采集二次激发后的聚焦信号,建立了聚焦信号幅值与螺栓预紧力的关系。实验结果显示,聚焦信号的幅值随着螺栓预紧力的增大而增大;当预紧力达到一定程度时聚焦信号会出现饱和现象;通过提高螺栓联接结构接触面粗糙度与接触面受力状态,能将饱和现象有效后移甚至消除,进而实现对整个螺栓额定载荷范围内螺栓预紧力的检测。基于压电时间反演法的螺栓松动检测技术在螺栓联接状态监测方面具有很好的应用前景。

The piezoelectric time reversal method is used for bolt looseness detection. Experiments are conductedon bolt joints. Two piezoelectric patches are respectively bonded on the two different sides of a bolt joint used as ac-tuator generating ultrasonic signal and sensor. Using its self-adaptive focusing and high signal to noise ratio of thetime reversal technique,the received response signal is reversed in time domain and then is reemitted as an excita-tion signal to acquire time reversal focusing signals. The relationship between the time reversal focusing signal am-plitude and the bolt preload is achieved. The experiment results show that the time reversal focusing signal ampli-tude will increase with bolt preload increase. When bolt preload increase to a certain saturation value,the focusingsignal amplitude will remain unchanged. By increasing the contact surface roughness of bolt joint and the distanceof the bolt and piezoelectric patch,the saturation force will be delayed,thus the proposed piezoelectric time reversalmethod can measure the whole range of bolt preload. The experiments show that the piezoelectric time reversalmethod for bolt looseness detection has a good prospect application in bolt connection health monitoring.